1. Field of the Invention
The present invention concerns a simulator that is suitable for use with a breathing-assist apparatus that monitors and/or controls the breathing of a patient.
2. Description of the Prior Art
Ventilators are commonly used to provide assisted breathing to patients. The breathing support provided by a ventilator may be controlled in different ways to ensure appropriate ventilation of the patient. Traditionally the breathing support is based on measurements on the patient's ventilation, that is, air pressure and/or air flow in the patient's lungs, and the support is triggered by detection of the inspiratory efforts of the patient. The pressure or air flow must be measured continuously and it may be difficult to determine which part of the signal originates from the patient.
A breathing effort is controlled by the breathing centre in the brain, the main breathing muscle, the diaphragm, is activated through nerve transmission in the phrenic nerve. When the muscle is activated, it contracts and lowers the pressure in the thorax and thus creates an inspiratory flow.
A novel development in the field of ventilation improves the ventilator's responsiveness to the patient breathing efforts by sensing the inspiratory effort by detecting the electric activity, the electromyogram (EMG), of the contracting diaphragm. The electromyographic signal is picked up using an oesophageal array of electrodes. The signal is conditioned and a signal representative of the diaphragmal electrical activity, the EAdi, a is calculated. The supply of gas from the ventilator to the patient is then controlled in a suitable manner in proportion to the EAdi, in most cases the pressure delivered to the patient is controlled.
EP 1 205 202 discloses an EMG controlled ventilator system, but said system does not propose a way of ensuring that the units providing the EMG control of the ventilator actually work and provide correct signals.
Instead of EMG, another bioelectric signal indicative of the patient's breathing efforts may be used to control the ventilation. The new technology of EMG, or other bioelectric signal, controlled ventilation provides a powerful tool for physicians and medical personal working with patients in need of ventilation support, however it also causes new problems and challenges.
Apart from the new modes of ventilation, new equipment such as oesophageal probes or other sensors for detecting EMG or bioelectric signals representing respiratory activity is needed in to use the new technology.
The new requirements above calls for a solution to facilitate the work and improve the understanding for medical personnel and other professionals who use, produces, tests and develops ventilators controlled by EMG or bio-electric signals representing respiratory activity.